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<app-root ng-version="20.1.4" _nghost-ng-c2830357685 ngh="3" ng-server-context="ssg"><div _ngcontent-ng-c2830357685 class="page-splash"><div _ngcontent-ng-c2830357685 class="mast"><div _ngcontent-ng-c2830357685><div _ngcontent-ng-c2830357685 class="mast-logo"><a _ngcontent-ng-c2830357685 href="/"><img _ngcontent-ng-c2830357685 src="/assets/images/djongo-symbol-small.png" alt="Djongo"></a><!----></div><div _ngcontent-ng-c2830357685 class="mast-nav"><app-nav _ngcontent-ng-c2830357685 _nghost-ng-c40719357 ngh="0"><!----><!----><!----></app-nav></div></div></div><div _ngcontent-ng-c2830357685 class="initial-content"><router-outlet _ngcontent-ng-c2830357685></router-outlet><ng-component _nghost-ng-c2001800090 ngh="2"><div _ngcontent-ng-c2001800090 class="body"><aside _ngcontent-ng-c2001800090 class="nav-sticky aside-left"><app-nav _ngcontent-ng-c2001800090 _nghost-ng-c40719357 ngh="0"><!----><!----><!----></app-nav></aside><div _ngcontent-ng-c2001800090 class="page-content"><header _ngcontent-ng-c2001800090><h1 _ngcontent-ng-c2001800090 class="title-docs">Using Djongo Array Field</h1></header><router-outlet _ngcontent-ng-c2001800090></router-outlet><using-djongo-array-field-1 class="3" ngh="1"><h2 id="arrayfield">ArrayField</h2><p>With Djongo there can be an <a href="https://docs.mongodb.com/manual/core/document/#arrays">array</a> of embedded documents inside the parent document. You can create an <strong>embed array/list of models inside the parent model</strong> and store it directly into MongoDB.</p><h3 id="example">Example</h3><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="kn">from</span> <span class="nn">djongo</span> <span class="kn">import</span> <span class="n">models</span>
<span class="kn">from</span> <span class="nn">django</span> <span class="kn">import</span> <span class="n">forms</span>

<span class="k">class</span> <span class="nc">Blog</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
    <span class="n">tagline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">()</span>

    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">abstract</span> <span class="o">=</span> <span class="kc">True</span>

<span class="k">class</span> <span class="nc">BlogForm</span><span class="p">(</span><span class="n">forms</span><span class="o">.</span><span class="n">ModelForm</span><span class="p">):</span>
    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">model</span> <span class="o">=</span> <span class="n">Blog</span>
        <span class="n">fields</span> <span class="o">=</span> <span class="p">(</span>
            <span class="s1">'name'</span><span class="p">,</span> <span class="s1">'tagline'</span>
        <span class="p">)</span>

<span class="k">class</span> <span class="nc">Author</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">200</span><span class="p">)</span>
    <span class="n">email</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmailField</span><span class="p">()</span>

    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">abstract</span> <span class="o">=</span> <span class="kc">True</span>

<span class="k">class</span> <span class="nc">AuthorForm</span><span class="p">(</span><span class="n">forms</span><span class="o">.</span><span class="n">ModelForm</span><span class="p">):</span>
    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">model</span> <span class="o">=</span> <span class="n">Author</span>
        <span class="n">fields</span> <span class="o">=</span> <span class="p">(</span>
            <span class="s1">'name'</span><span class="p">,</span> <span class="s1">'email'</span>
        <span class="p">)</span>

<span class="k">class</span> <span class="nc">Entry</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">blog</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmbeddedField</span><span class="p">(</span>
        <span class="n">model_container</span><span class="o">=</span><span class="n">Blog</span><span class="p">,</span>
        <span class="n">model_form_class</span><span class="o">=</span><span class="n">BlogForm</span>
    <span class="p">)</span>

    <span class="n">headline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">)</span>    
    <span class="n">authors</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ArrayField</span><span class="p">(</span>
        <span class="n">model_container</span><span class="o">=</span><span class="n">Author</span><span class="p">,</span>
        <span class="n">model_form_class</span><span class="o">=</span><span class="n">AuthorForm</span>
    <span class="p">)</span>

    <span class="n">objects</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DjongoManager</span><span class="p">()</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><h3 id="creating-array-fields">Creating Array fields</h3><p>A Model with an Array field can be created as follows:</p><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="n">entry</span> <span class="o">=</span> <span class="n">Entry</span><span class="p">()</span>
<span class="n">entry</span><span class="o">.</span><span class="n">authors</span> <span class="o">=</span> <span class="p">[{</span><span class="s1">'name'</span><span class="p">:</span> <span class="s1">'John'</span><span class="p">,</span> <span class="s1">'email'</span><span class="p">:</span> <span class="s1">'john@mail.com'</span><span class="p">},</span>
                <span class="p">{</span><span class="s1">'name'</span><span class="p">:</span> <span class="s1">'Paul'</span><span class="p">,</span> <span class="s1">'email'</span><span class="p">:</span> <span class="s1">'paul@mail.com'</span><span class="p">}]</span>
<span class="n">entry</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><h3 id="querying-array-fields">Querying Array fields</h3><p>Djongo uses a mixture of Django query syntax and MongoDB query syntax. Consider a query to retrieve all entries made by the author <em>Paul</em>. Using <code>ManyToManyField</code> this requires 2 SQL queries. First selects the <code>id</code> for author Paul from the <code>author</code> table. Next, a JOIN with <code>entry_authors</code> and <code>entry</code> gives the corresponding entries. </p><p>With <code>ArrayField</code> the query reduces to a single simple query: </p><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="n">entries</span> <span class="o">=</span> <span class="n">Entry</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">authors</span><span class="o">=</span><span class="p">{</span><span class="s1">'name'</span><span class="p">:</span> <span class="s1">'Paul'</span><span class="p">})</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><p>Djongo lets you get even more specific with your queries. To query all entries where the <em>third author is Paul</em>:</p><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="n">entries</span> <span class="o">=</span> <span class="n">Entry</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">authors</span><span class="o">=</span><span class="p">{</span><span class="s1">'2.name'</span><span class="p">:</span> <span class="s1">'Paul'</span><span class="p">})</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><p>Note: In MongoDB the first element in the array starts at index 0.</p><h2 id="using-arrayfield-in-django-admin">Using ArrayField in Django Admin</h2><p>The official <a href="https://docs.djangoproject.com/en/2.0/topics/db/queries/">Django documentation</a> exemplifies 3 models that interact with each other: <strong>Blog, Author and Entry</strong>. This tutorial considers the same 3 models. The <code>blog</code>; <code>ForeignKey</code> of the <code>Entry</code> model was optimized in the <a routerlink="/using-django-with-mongodb-data-fields/" href="/using-django-with-mongodb-data-fields" jsaction="click:;">other tutorial</a>, here we optimize the <code>authors</code>; <code>ManyToManyField</code>.</p><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="kn">from</span> <span class="nn">djongo</span> <span class="kn">import</span> <span class="n">models</span>

<span class="k">class</span> <span class="nc">Blog</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
    <span class="n">tagline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">()</span>

    <span class="k">def</span> <span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>

<span class="k">class</span> <span class="nc">Author</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">200</span><span class="p">)</span>
    <span class="n">email</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmailField</span><span class="p">()</span>

    <span class="k">def</span> <span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>

<span class="k">class</span> <span class="nc">Entry</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">blog</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ForeignKey</span><span class="p">(</span><span class="n">Blog</span><span class="p">,</span> <span class="n">on_delete</span><span class="o">=</span><span class="n">models</span><span class="o">.</span><span class="n">CASCADE</span><span class="p">)</span>
    <span class="n">headline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">)</span>
    <span class="n">body_text</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">()</span>
    <span class="n">pub_date</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateField</span><span class="p">()</span>
    <span class="n">mod_date</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateField</span><span class="p">()</span>
    <span class="n">authors</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ManyToManyField</span><span class="p">(</span><span class="n">Author</span><span class="p">)</span>
    <span class="n">n_comments</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>
    <span class="n">n_pingbacks</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>
    <span class="n">rating</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>

    <span class="k">def</span> <span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">headline</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><p>A <code>ManyToManyField</code> defines a relation wherein <em>an entry is made by several authors</em>. It also defines a relation wherein <em>an author could have made several entries</em>. Django handles this internally by <strong>creating another table</strong>, the <code>entry_authors</code> table which contains different mappings between <code>entry_id</code> and <code>author_id</code>.</p><p>Fetching an entry will require 2 SQL queries. The second query will be an expensive JOIN query across <code>entry_authors</code> and <code>authors</code>. The Model described above will work perfectly well on MongoDB as well, when you use Djongo as the connector. MongoDB however offers much more powerful ways to make such queries. These queries come at the cost of higher disk space utilization.</p><p>As a designer using Djongo, you have the freedom to continue with the above schema. Alternatively, you can define a schema having a trade off on disk space for higher performance.</p><p>Let us redefine the <code>authors</code> in the <code>Entry</code> models using the <code>ArrayField</code>:</p><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="kn">from</span> <span class="nn">djongo</span> <span class="kn">import</span> <span class="n">models</span>

<span class="k">class</span> <span class="nc">Blog</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
    <span class="n">tagline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">()</span>

    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">abstract</span> <span class="o">=</span> <span class="kc">True</span>

<span class="k">class</span> <span class="nc">MetaData</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">pub_date</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateField</span><span class="p">()</span>
    <span class="n">mod_date</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">DateField</span><span class="p">()</span>
    <span class="n">n_pingbacks</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>
    <span class="n">rating</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>

    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">abstract</span> <span class="o">=</span> <span class="kc">True</span>

<span class="k">class</span> <span class="nc">Author</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">200</span><span class="p">)</span>
    <span class="n">email</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmailField</span><span class="p">()</span>

    <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
        <span class="n">abstract</span> <span class="o">=</span> <span class="kc">True</span>

    <span class="k">def</span> <span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>

<span class="k">class</span> <span class="nc">Entry</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
    <span class="n">blog</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmbeddedField</span><span class="p">(</span>
        <span class="n">model_container</span><span class="o">=</span><span class="n">Blog</span><span class="p">,</span>
    <span class="p">)</span>
    <span class="n">meta_data</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">EmbeddedField</span><span class="p">(</span>
        <span class="n">model_container</span><span class="o">=</span><span class="n">MetaData</span><span class="p">,</span>
    <span class="p">)</span>

    <span class="n">headline</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">255</span><span class="p">)</span>
    <span class="n">body_text</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">TextField</span><span class="p">()</span>

    <span class="n">authors</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">ArrayField</span><span class="p">(</span>
        <span class="n">model_container</span><span class="o">=</span><span class="n">Author</span><span class="p">,</span>
    <span class="p">)</span>
    <span class="n">n_comments</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>

    <span class="k">def</span> <span class="fm">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">headline</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><p><strong>Notice</strong> how the <code>ManyToManyField</code> is now replaced by the <code>ArrayField</code>. To display the Array field in Django Admin, a <code>Form</code> for the field must be present. Since the array is made up of abstract <code>Author</code> models, the form can be easily created by using a <code>ModelForm</code>. If you do not specify a <code>ModelForm</code> for your array models in the <code>model_form_class</code> argument, Djongo will automatically generate a <code>ModelForm</code> for you.</p><p><img alt="Array-model-field" src="/assets/images/array-model-field.png"></p><blockquote><p>Django Admin reveals multiple neatly nested <code>Name</code> and <code>Email</code> fields under a single Author label.</p></blockquote><p>Retrieving an entry from the database will result in <strong>no JOINS and only a single database lookup. It is super fast</strong></p><h2 id="api-reference">API Reference</h2><div appcodecopy class="highlighter-rouge highlight codehilite"><pre><span></span><code><span class="k">class</span> <span class="nc">ArrayField</span><span class="p">(</span><span class="n">MongoField</span><span class="p">):</span>
    <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span>
                 <span class="n">model_container</span><span class="p">:</span> <span class="n">typing</span><span class="o">.</span><span class="n">Type</span><span class="p">[</span><span class="n">Model</span><span class="p">],</span>
                 <span class="n">model_form_class</span><span class="p">:</span> <span class="n">typing</span><span class="o">.</span><span class="n">Type</span><span class="p">[</span><span class="n">forms</span><span class="o">.</span><span class="n">ModelForm</span><span class="p">]</span> <span class="o">=</span> <span class="kc">None</span><span class="p">,</span>
                 <span class="n">model_form_kwargs</span><span class="p">:</span> <span class="nb">dict</span> <span class="o">=</span> <span class="kc">None</span><span class="p">,</span>
                 <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
</code></pre><img alt="copy code" src="/assets/images/copy.svg" class="docs-copy"></div><h3 id="arguments">Arguments</h3><table><thead><tr><th>Argument</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><code>model_container</code></td><td><code>models.Model</code></td><td>The child model class type (not the instance) that this array field will contain.</td></tr><tr><td><code>model_form_class</code></td><td><code>models.forms.ModelForm</code></td><td>The child model form class type of the array model. All child models inside the array must be of the same type. Mixing different types of child models inside the embedded array is not supported.</td></tr><tr><td><code>model_form_kwargs</code></td><td><code>dict()</code></td><td>The kwargs (if any) that must be passed to the <code>forms.ModelForm</code> while instantiating it.</td></tr></tbody></table></using-djongo-array-field-1><!----></div><aside _ngcontent-ng-c2001800090 class="nav-sticky aside-right"><nav _ngcontent-ng-c2001800090 class="nav nav-toc"><h3 _ngcontent-ng-c2001800090><i _ngcontent-ng-c2001800090 class="fas fa-file-alt"></i> On This Page</h3><ul _ngcontent-ng-c2001800090><!----></ul></nav></aside><aside _ngcontent-ng-c2001800090 class="nav-sticky aside-right-2"><nav _ngcontent-ng-c2001800090 class="nav"><ul _ngcontent-ng-c2001800090><li _ngcontent-ng-c2001800090><a _ngcontent-ng-c2001800090 class="btn btn-invert btn-green-invert btn-nav" href="/docs/1.3/get-started" jsaction="click:;"> 1.3 </a></li><li _ngcontent-ng-c2001800090><a _ngcontent-ng-c2001800090 class="btn btn-invert btn-green-invert btn-nav" href="/docs/2.0/get-started" jsaction="click:;"> 2.0 </a></li><!----></ul></nav></aside></div></ng-component><!----></div><div _ngcontent-ng-c2830357685 id="footer" class="page-footer"><footer _ngcontent-ng-c2830357685><aside _ngcontent-ng-c2830357685 class="l-fixed-notice cookie-notice open"><p _ngcontent-ng-c2830357685>We use cookies to enhance user experience. You consent to their usage by browsing this site. <button _ngcontent-ng-c2830357685 id="cookie-accept" class="btn btn-green" jsaction="click:;">Accept</button></p></aside><div _ngcontent-ng-c2830357685 class="page-footer-copyright">© 2025 Doableware AB.</div></footer></div></div></app-root>
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